1. Field of the Invention
The present invention relates to actuators, and particularly to a torque converter that converts a given input torque into higher torque.
2. Description of the Related Art
A typical rotary actuator, especially a hydraulic type rotary actuator, utilizes mating helical components to convert linear motion into rotary motion. The helical components include a piston sleeve that has a helix formed on both outer and inner surfaces. The inner helix of the piston is mated to an outer helix on a rotary drive shaft, while the outer helix on the piston is mated to a fixed inner helix of the actuator housing. When hydraulic force acts on the face of the piston, this causes the piston to reciprocate within the housing and rotate the drive shaft.
A theoretical work output (W) for this type of rotary actuator is determined by the hydraulic force (F) acting on the piston multiplied by the travel distance of the piston (S), as represented by the equation, W=F×S. The total work (Wwork total) for this actuator can be converted into output torque (Ttorque output), as represented by the equation, Wwork total=Ttorque output. Note that for a given force input, the input force acting on the piston face increases proportionally with the area of the face, since seals and the housing limit the maximum hydraulic pressure. Therefore, the relationship between the piston area and the piston travel distance determine work output or torque, and helical factors have no bearing on this relationship.
Although compact and efficient, such a rotary actuator does not produce the full potential of its piston configuration. For example, the face of the piston is annular, which is much less area than the cross section of the housing. The compact nature of the actuator and the relatively large pitch angle employed therein also limits the travel distance of the piston. These factors reduce the potential work output. Moreover, this type of actuator is relatively difficult to manufacture due, in part, to the various helixes that need to be machined or formed, both inside and outside the various components. The nature and work of these actuators also require a variety of specialized seals to prevent leakages in high-pressure fluid environments. Furthermore, these actuators are typically custom-made for particular applications. There are no set standards for producing these types of actuators, which limits customization and expansion without resorting to more costly expenses of custom manufacture.
There is a need for a piston-type actuator that can more fully maximize work or torque output within a relatively compact and simple device. Thus, a torque converter solving the aforementioned problems is desired.